Traditionally, when photographing a reflective object, such as a car, in a real environment, like a park or on a mountain or inside a building, a photographer takes a picture of the car with the background behind. All of the reflections in the surfaces, e.g. sheet metal and chrome and glass, are naturally gathered by the real vehicle.
If a photographer photographs a background image with the intent of rendering a computer generated image (CGI), for example of the car, into the scene, then the entire reflection and luminance data of the scene at the time of taking the background picture is typically gathered. To understand the problem, think of a car as a mirror with all of its surfaces reflecting the environment. Some surfaces are chrome, mirror like, others show the environment reflected in the color of the paint.
In creating spherical imagery of automobiles spherical (360×180 degree) high dynamic range (HDR) imagery is used as reflection and luminance data when rendering an automotive wire frame to create a photographic representation of that wire frame vehicle. The HDR imagery is a ball-like picture, a sphere, that contains the reflections of the scene, e.g. what is reflected onto the car paint, as well as the luminance of the scene. The luminance of the scene can then be used to “light” the CGI paint and chrome and glass, e.g. shaders, to match the exact light color of the environment.
This HDR spherical image is then wrapped around a wire frame computer model of a car in a 3D program such as 3Dmax, available from Autodesk, Inc. of San Rafael, Calif. or Maya, available from Alias Research of Toronto, Canada. When texture shaders are applied to the wire frame to represent chrome and glass and metal, they react to the HDR spherical image to create a rendering of the vehicle that looks natural and is reflecting the environment to match the background image.
Traditional approaches to obtaining HDR spherical images have involved linear optical sensors that rotate about a vertical axis. Examples of such “spherical cameras” include the Panoscan MK-3 from Panoscan, Inc. of Van Nuys, Calif. and the SpheroCam HDR from SpheronVR AG. of Waldfischbach-Burgalben, Germany. They both use fish-eye 180 degree lenses on a horizontally rotating camera to create the 360 degree image of the environment. The Panoscan achieves HDR by rotating three times to make the layers necessary for HDR. The SpheroCam HDR uses several successive exposures from a single scan line in a chip, before rotating to the next minute scan position.
The costs of these cameras are high, creating a serious barrier to entry for a photographer into many fields, including the field of CGI automotive background photography. Both cameras require attachment to computers and are too delicate or time consuming to set-up for work in the demanding area of location car photography.